I took ddi for about 3 years when it first came out.(from 1990 thru 1993, I think). Around 1993, my doctor thought I was becoming resistant to it since my t-cells started to drop. I had a resistance test in Feb. 2000 which did not show any ddi resistance. I had been told that it is possible for resistance to go away once the drug has been stopped for a period of time, but I'm not sure how much time. Also that once you have been resistant to a drug, even if that resistance (mutation) disappears, it can come back because there may be small amounts of that resistant strain lurking somewhere, which would tend to reoccur once the drug is started again. So, my question is twofold: 1.)Could I now have developed resistance to ddi again now that I have been back on it for 10 months? 2.)In Feb. of this year, the test showed that I was resistant to Sustiva, Viracept, AZT, & 3TC. Now that I have been off them for a while (a year or more) can those mutations have disappeared like the ddi mutation did? And if so, could I possibly go back on some of those drugs? My viral load is undetectable so I would have to go off meds for about a month to get enough virus to perform another resistance test, which is what I did in Feb. Is there any danger in stopping meds for a month every year or so? Also, does Kaletra have any cross resistance with other PI's? I know I've asked a lot of questions, but any information on this would be extremely helpful. Thank you.

Response from Dr. Holodniy

Hard to know whether you had developed ddI resistance the first time you were on it. It has been difficult to document resistance to ddI in people. You are correct though, that people who demonstrate resistance, when taken off those drugs will see that resistance disappear. Thus, in your case going off meds will not help determine whether you have resistance or not. It DOES NOT go away. It fades to the background and is below the detection of current resistance assays. Going back on those meds to which your virus had resistance, will result in the resistance coming back in a shorter time. Kaletra has had success in people with PI resistance. However there appears to be a threshold effect, in that if there are several critical PI mutations, then Kaletra will not work.

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